TJM obs of 2007 Jul 12 UTC

From: Ted Molczan (sslmolcz@rogers.com)
Date: Thu Jul 12 2007 - 12:32:35 EDT

  • Next message: Ted Molczan: "TJM obs of 2007 Jul 12 UTC"

    This is an update of a message sent hours ago, that has yet to make it to the
    list.
    
    I observed the recently launched NOSS 3-4 pair, after a 23 day period without
    observations:
    
    31701 07 027A   2701 G 20070712084530620 17 25 0127403-104836 47 S
    31708 07 027C   2701 G 20070712084605500 17 25 0127030-104260 87 S
    
    IOD format: http://www.satobs.org/position/IODformat.html
    
    Site 2701: 43.68764 N, 79.39243 W, 230 m
    
    Assuming they have not traded places, the A object, which was the leader, was
    198 s late, and about 0.08 deg higher in track than predicted by my 23 day old
    elements, listed below. The C object was 118 s late, and 0.1 deg higher than
    predicted. The track differences take into account Earth's rotation in the
    interim of the prediction time error. C trailed A by about 35 s.
    
    NOSS 3-4 (A)     0.0  0.0  0.0  4.9 v
    1 31701U 07027A   07170.06979759  .00000020  00000-0  20000-4 0    06
    2 31701  63.3811  37.1588 0232911 148.8868 212.6203 13.65676455    03
    
    NOSS 3-4 (C)     0.0  0.0  0.0  4.9 v
    1 31708U 07027C   07170.06992739  .00000020  00000-0  20000-4 0    06
    2 31708  63.3479  37.1783 0231929 151.1831 210.2249 13.65605473    08
    
    Below are estimated NOSS 3-4 elements, based on the hunch that both satellites
    have manoeuvred once since last observed on June 19, by Scott Campbell, mainly
    to achieve station-keeping.
    
    During Scott's obs of June 19, they were separated by some 15 s, compared with
    34.88 s during my obs. Their orbits of June 19 would have resulted in
    approximately the separation I observed, by June 24, near 09:00 UTC. Assuming
    they manoeuvred at the nearest apogee, around 09:48 UTC, to slightly raise their
    perigee and nearly match mean motion, I obtain the following approximate
    elements:
    
    1 71701U          07175.40826389  .00000020  00000-0  20000-4 0    07
    2 71701  63.3811  22.9394 0232000 148.9211 178.8500 13.65502500    08
    
    1 71708U          07175.40913194  .00000020  00000-0  20000-4 0    05
    2 71708  63.3479  22.9423 0231400 151.2542 178.7500 13.65501000    08
    
    Basically, I precessed my June 19 elements to the above epochs, and then
    adjusted mean motion by trial and error to closely predict the passes I observed
    this morning. I also adjusted eccentricity to hold the apogee distance constant.
    
    
    That nearly identical mean motions result, tends to support my hunch. If it is
    correct, then the above should be accurate to within a few seconds, and
    reasonably close in track, within 24 h of my obs of this morning.
    
    Ted Molczan
    
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